The present invention generally relates to a method and apparatus for detecting objects in a video frame and, more particularly, to a method and apparatus for detecting players and a ball in soccer videos by using color segmentation and shape analysis techniques.
In soccer videos, the soccer players and the ball are the most important objects in that they represent a large amount of information about each instant of a game. Detection and tracking of the players and the ball have been motivated by various applications, such as event detection, tactics analysis, automatic indexing/summarization, and object-based compression.
Known methods for locating the ball as well as the players in soccer videos can be divided in two distinct groups: the first group of methods makes use of fixed cameras, usually calibrated in advance, in a controlled environment, whereas the second group of methods employs regular broadcast videos. While the former can provide better performance, the latter appear to be more flexible.
Since soccer is a spectator sport, the playing field, the lines, the ball, and the uniforms of the players are designed to be visually distinctive in color. In spite of this visual distinctiveness, detection of the players and the ball is not without error. Some approaches in the second group of methods have attempted to mitigate detection difficulties by finding the grass playing field first through the use of color segmentation and post-processing with morphological operations, such as connected component analysis, in order to limit the search area. But errors still occur. Errors can be categorized at least as false alarms and as artifacts. A false alarm refers to the identification and detection of a non-player as a player or the identification and detection of a non-ball as the ball. An artifact arises when the lines on the playing field, for example, merge with portions of a detected player.
Additional difficulties and potential errors arise when the players overlap because the foreground shape becomes complex. In this situation, identification and separation of overlapped players is a challenging problem that has not been addressed to date.
Accordingly, there is a need for a method for substantially eliminating errors that occur in the detection of foreground objects such as players and a ball, for example, in video images including those objects.